Heat responsive snap acting switch



Nov, 1, 1966 J. LlEBERMANN ET AL 3,283,099

HEAT RESPONSIVE SNAP ACTING SWITCH 5 Sheets-Sheet 1 Filed Jan. 15, 1965 INVENTOR OHN LIEBERMANN DONALD L. CONING A RNEY Nov. 1, 1966 J. LIEBERMANN ET AL 3,233,099

HEAT RESPONSIVE SNAP ACTING SWITCH Filed Jan. 15, 1965 Sheets-Sheet 2 Fig. 2

INVENTOR JOHN LIEBERMANN DONALD L. (ZONING BY f? 2' A ORNEY Nov. 1, 1966 J. LIEBERMANN ET 3,283,099

HEAT RESPONSIVE SNAP ACTING SWITCH Filed Jan. 15. 1965 5 Sheets-Sheet 5 INVENTOR JOHN LIEBERMANN DONALD L. CONING Nov. 1, 1966 J. LIEBERMANN ET AL 3,283,099

HEAT RESPONSIVE SNAP ACTING SWITCH Filed Jan. 15. 1965 5 Sheets-Sheet 4 Fig.6

JOHN LIEBERMANN DONALD Lv CONING \sw'ms 5 Sheets-Sheet 5 R Y E WW A O VMN "H NR ,0. 21 m I. l u D C l L NA f u HN Q0 2 JD LIEBERMANN ET Novc. 1, 1966 J.

HEAT RESPONSIVB SNAP ACTING SWITCH Filed Jan. 15, 1965 United States Patent C) 3,283,099 HEAT RESPllNSIVE NAP ACTENG SWITCH John Liebermann, Columbus, and Donald L. (Zoning, Gahanua, Ohio, assignors t Rance Incorporated, Columbus, Uhio, a corporation of Ohio Filed Jan. 15, 1965, Ser. No. 425,883 Claims. (Cl. 2ti)140) The present invention relates to pressure responsive electric switching mechanisms particularly suitable for use as adjustable thermostatic control devices for air conditioning equipment and the like.

More particularly the present invention relates to an improvement in a control device for air cooling apparatus or the like comprising a housing supporting an electric switch to be connected in the circuit of the refrigerant compressor motor of the apparatus and which is actuated by an expandable power element having a temperature sensing tube connected therewith and filled with a vapor which changes in pressure according to changes in temperature. The housing is supported on a panel or the like of the air cooling apparatus and a control knob projects therefrom which the user may conventiently manipulate to set the control device to cause continual operation of the apparatus, or to adjust temperatures at which the apparatus is cyclically operated, or to turn the apparatus off, or to control the circuit of an electric fan for circulating air to be cooled through the apparatus. The invention provides a construction by which a rela- =tively few parts, easily fabricated, are utilized to provide the control device, and by use of many common parts, different modifications of the control may be manufactured. For example, one form may have the control knob shaft projecting from the same wall of the housing as does the temperature sensing tube and in another form the control knob shaft may project from a wall of the housing which is at right angles to the wall from which the tube extends, the different forms being available for use on differently arranged air cooling apparatus.

In carrying out the invention, it is an object to provide an electric switch operated by a pressure responsive element through a single elongated resilient beam which serves to variably load the element and also to amplify movements thereof to actuate the switch, one end of the beam being pivoted adjacent the power element and the opposite end being supported on a lever which is shiftable about its pivot by a cam attached to a rotatable adjusting shaft supported in an opening in one wall of the housing and which cam is engaged by a portion of the lever extending parallel to the beam, the cam having a contour such that when it is rotated to one position the lever is shifted to alter the loading of the beam on the power element in excess of the pressures normally developed by the power element to hold the switch in one control position irrespective of normal temperatures sensed by the power element and to relieve the beam when the cam is in another position whereby the beam is prevented from moving the switch to another switch operating posit-ion, irrespective of the reductionin pressure of the power element so as to provide constant running of the apparatus. In one form of control device the beam engaging lever includes an arm arranged to engage the beam during one portion of the travel of the lever to positively actuate the switch mechanism independently of the pressures in the power element.

Other objects and advantages of the invention will be apparent from the following description of a preferred form thereof, reference being made to the accompanying drawings wherein:

FlG. l is an exploded view of one form of control device embodying the invention and which is particularly 3,283,69 Patented Nov. 1, 19%6 suited to control operation of an air conditioning apparatus;

FIG. 2 is a sectional view of the switch shown in FIG. 1 taken substantially along lines 22 of FIGS. 1 and 3, certain parts being broken away;

FIG. 3 is a sectional view of the control device taken substantially along line 33 of FIG. 2;

FIG. 4 is a fragmentary view of the device shown in FIG. 1;

FIG. 5 is a fragmentary sectional view taken substantially along line 55 of FIG. 2;

FIG. 6 is an exploded view of a second form of the invention;

FIG. 7 is a sectional view taken substantially along line 77 of FIG. 6; and

FIG. 8 is a sectional view taken along line 8-8 of Referring to FIGS. 1 through 5, a temperature control device embodying one form of the invention is shown at 10 which is particularly suitable for controlling the operation of a conventional air conditioning or cooling apparatus, not shown, comprising an electric motor driven refrigerant compressor, a refrigerant condenser and an evaporator all connected in the usual circuit to cool air circulated over the evaporator and into the space to be cooled by an electric motor driven fan. The control device comprises a rectangular box-like housing 11 formed of sheet metal and which is open at the bottom side, as viewed in the drawings. The bottom side of the housing is closed by a base 12 formed of a panel of suitable relatively rigid molded plastic material and which is secured in place by four rectangular lugs 12a formed thereon which fit into corresponding openings 11a in the front and rear walls of housing 11, only two of which appear in the drawings, the lugs being secured in the openings by crimping the wall portions along the lower edges of the openings against the lugs as is indicated at 11b in FIG. 2.

A snap acting switch mechanism 13 is supported on base 12 and it may be of any suitable form; that disclosed, however, comprises three terminal members 14, 15 and 16 having blade type terminal portions 14a, 15a and 16a which extend through and are suitably secured in openings through the base. Terminal 14 has a bridge like section 14b on the inside surface of the base to which a fixed switch contact 13a is secured. An upstanding insulating plate 14c is attached to terminal portion 14a and has a rectangular window 14d therethrough forming upper and lower limiting stops for the arm of a snap mechanism described more fully hereinafter.

A flat spring type contact arm 13b is riveted at one end to a bridge portion 15b of terminal member 15, and a switch contact 13c is attached to the opposite end of the contact arm, which arm is inherently biased to urge contact to engage contact 130:.

Contact arm 13b is actuated and controlled in move ment by an actuator arm 17 which is formed of a fiat spring strip having one end riveted to bridge portion 15b and overlapping the fixed end of contact arm 11% and the opposite end of which has a tongue 17a which extends loosely through an opening in an upturned tab 13d of contact arm 13b and through window 14d. The opening through tab 13d provides a lost motion connection between arms 17 and 13b.

Arm 17 is snap actuated between the limits formed by the upper and lower edges of window 14d by a toggle tongue 17b formed integral with the arm and the projecting end of Which is pivoted in a V groove extending across the face of a cantilever abutment 15c projecting from the bridge portion 15b, the tongue being bowed to exert a spring force in the direction of the movable end of "arm 17. Arm 17 is inherently biased upwardly for overcoming the closing bias of arm 13b and moving that arm to separate contacts 13a and 130 to open the switch, and is moved downwardly to permit contact arm 13 to close the contacts by the depression of an insulator button 18 which is riveted to a cross member of the actuator arm. Snap movements are imparted to arm 17 by tongue 17b shifting its line of force from above and below a plane through the centerline of the arm 'as the arm moves above or below the plane of the pivot points at the end of the tongue. This snap movement is transmitted to contact arm 13 by a hammer blow action by reason of the lost motion connection between the two arms: Thus, the contacts 13a and 13c are opened and closed with a rapid, decisive movement to minimize arcing and prevent sticking of the contacts.

It will be seen that by depressing button 18, switch contacts 13a and 130 are closed and :a circuit can be established through terminal 14, contacts 1311, 13c, contact arm 13b and terminal 15. When button 18 is released arm 17 moves upwardly with a snap action causing contacts 13a and 130 to break the aforementioned circuit with a snap movement.

Switch actuator button 18 is depressed to switch closing position by expansion of a pressure responsive power element 20 acting through a resilient beam 21. Power element 20' comprises a wafer type bellows formed of two dish shaped flexible metal discs or diaphragms 20a and 20b suitably sealed together at their edges to form an expansible chamber. Diaphragm 20b is brazed to a rigid base plate 22 to which one end of a capillary tube 20c is brazed to communicate with the interior of the bellows, and the outer end of which tube is sealed as at 20d. Bellows 20 secured to plate 22 is inserted into housing 11 through a rectangular opening 11a in the rear wall 11b thereof, as viewed in FIG. 1, and a slot 110 in the top wall 11d of the housing receives tube 200. The opening 11a is closed by a flange 22a formed on plate 22 and which is secured to the housing by two lugs 11c extending from the rear wall of the housing and engaging in notches in flange 22a, and a tab 22b projecting through an opening in top wall 11d. A positioning lug 220 formed on plate 22 projects into slot 11c.

The bellows 20 and tube 200 contain a suitable vapor, such as a refrigerant well known as Freon, which expands and contracts with changes in temperature, thereby causing expansion and contraction of the bellows in accordance with temperatures at the tube. Preferably, the tube is located in a position which is normally cooler than the temperature at the bellows so that the pressure inside the bellows corresponds to the temperaature of the tube. The vapor content of the power element is limited so that it wvill be completely vaporized at a temperature slightly above the desired range of operation of the control device so that excessive pressures will never develop in the :bellows.

Expansion and contraction of bellows 20 is transmitted to switch actuator arm 17 through a resilient beam 21 against which button 18 rests, the movable wall 20a of the bellows having a rigid pointed stud 20c thereon which engages in the apex of a dimple formed in the beam to minimize friction between the engaging parts. Beam 21 comprises a strip of flat spring metal, one end of which rests on a abutment 11 formed by striking inwardly a portion of an end wall of housing 11 and the opposite end of the beam rests on a positionable support, described more fully hereinafter so that the spring beam urges the bellows toward a collapsed position whereby movement of button 18 to operate switch 13 occurs when pressures inside the bellows correspond to the temperatures desired to be maintained by the air conditionerr controlled by the switch, which is well understood by those familiar with the art.

Beam 21 has a rectangular opening 21a therethrough which is provided in the event the lever is to be used in a modified form of control apparatus described hereinafter and has a lug 57 formed thereon for a like purpose, as appears hereinafter. The left hand end of beam 21 has a reverse curve formed therein and the under surface of the turned end portion has a V groove 21a formed therein which receives the pointed end of a screw 23 threaded through an opening in the yoke 24a of a U shaped lever 24. The ends of the two legs 24b of lever 24 are pivoted in bearings formed by edges of wedge shaped openings Hg in the opposite side walls of housing 11 so that the lever can be rotated about these pivots to shift the end of the beam 21 and either increase or decrease the load on bellows 20 as the case may be. The control mechanism can be calibrated by adjustment of screw 23 by a tool inserted through an opening 12b through base 12.

Lever 24 is positioned about its pivot by a cam 26 which is engaged by an mm 240 formed on the lever and which is maintained against the cam by the reaction of beam 21 of the lever.

In the form of the control shown in FIGS. 1-5, cam 26 is mounted on a shaft 27 which is rotatably supported in the front wall 11h of housing 11 and is adapted to have an adjusting knob attached thereto in a position on the air conditioner apparatus convenient to the user. The housing can be attached to a panel on the air conditioner by screws, not shown, extended through the panel and threaded into openings in embossments 11L Cam 26 includes a hub 26a to which shaft 27 is attached, and the shaft projects through an opening in wall 11h which is smaller than the hub, and a flat U shaped spring 28 received in a groove about the shaft at the outside of wall 11h holds the hub to the wall of the housing and retains the shaft in the openings.

Cam 26 is limited in counterclockwise movement, as viewed in FIG. 1, by a stop lug 26b formed thereon and which engages a tab 11j struck inwardly from the front wall of the housing, and rotation of the cam in the opposite direction is limited by lug 26b striking a tab 11k struck inwardly from the front wall of the housing.

Cam 26 has three distinct peripheral sections at different distances from the axis thereof which rock lever 24 about its pivots to vary the deflection of beam 21. When lever 260 of cam 26 is positioned to be engaged by arm 24c of lever 24 the lever is positioned to cause the greatest relaxation of pressure on beam 21 and switch 12 will be closed at relatively low temperatures, generally below that capable of attainment by the air conditioner controlled so that in effect, this position of the cam effects constant running of the air conditioner. The segment 26d of the cam has a gradually sloping radius and when engaged by arm 24c lever 24 is pivoted to produce variations in flexure of beam 21 so as to provide a control range of normal operating temperatures of the air conditioner.

When section 26a of cam 26 is engaged by arm Me of lever 24, the lever is tilted to apply suflicient force against beam 21 and element 20 to prevent the element from ex- .panding to close switch 13 and, in effect, provides an oif control position of the control switch. It will be seen that "by transmitting the movement of the power element 20 to switch 13 through loading beam 21 and controlling the beam through lever 24 as described, an exceedingly simple structure is effective to provide in a single control knob the capability of setting the air conditioner for constant running, a cycling temperature control range, and an oif position.

By forming the reverse bend in beam 21 for engaging screw 23, the eflective length of the lever is greater than the longitudinal dimension of the control to provide a proper spring rate for loading the bellows to produce the range of operations desired.

Control device 10 also provides an auxiliary switch 30 for controlling a fan circuit, not shown, for circulating air through the air conditioner, and the operation of the auxiliary switch is also controlled by cam 26.

Fan switch 30 comprises a fixed contact 341a attached to one 'le-g 16b of a U-shaped bracket 160 formed on the upper end of terminal member 16 and which extends across base 11 spaced from the switch mechanism 13. Contact 30a is engaged by a movable contact 3% attached to the end of a fiat spring contact arm 30c lying in a plane parallel to the side walls of housing 11 and having an integral laterally extending base strip 39d riveted to bridge portion 15b and overlying actuator arm 17. Arm 300 is normally biased to close contacts 30a and 30b and is moved laterally to open the contacts by a raised portion 26 on cam 26 engaging an insulator button 302 secured to contact arm 30c and positioned to be engaged by the cam rise when the cam is rotated to the switch off end of its limit. Rise 26 and button 30a are located and dimensioned so that contact arm 30c remains in the switch closed position when arm 240 of lever 24 initially engages segment 26c of the cam, which effects opening of switch 13 and in this position of the knob K and cam 26 the fan is operated although the air conditioner compressor motor circuit is open through switch 13. Both the air conditioner and fan circuits can be opened by movement of the cam to bring rise 26 against button 30c.

Another form of air conditioner control embodying the invention is show-n at 50 in FIGS. 6 to 8 in which the axis of the control knob K is normal to the top wall of the housing, yet the principal parts of the control are like or basically like those described with reference to control 10 and such parts bear the same reference characters.

Control 50 comprises a housing 11 including a base 12 supporting a snap switch 13 which is actuated by a power element 20 through a beam 21, all as described with reference to control 10. The principal differences in the control structures lies in the arrangement by which beam 21 is deflected to provide various control functions and in the mounting mean-s, which in control 50 includes a laterally projecting taJb 11p having an opening therethrough, through which a mounting bolt may be located. Furthermore, the view of control 50 discloses a tab 11:; which is formed on an end wall of the housing and locks the end wall to the side wall by extending into an opening 111'.

The reversed end portion of beam 21 of control 50 is deflected by a lever 51 which is U shaped and has laterally extending pivot tabs 51a projecting from opposite sides of the yoke thereof and which are pivoted in wedge.shaped bearing openings 11m in the side wall of housing 11. Screw 51b is threaded through the yoke and engages beam 21 in the same manner as described relative to control device 10. Lever 51 is positioned about its pivot by a cam 53 which is located on the top side of wall 11d and is attached to a shaft 54 having an end extending through an opening in the top wall of housing 13 and secured in place by a fiat U spring 55 having the legs thereof received in a groove around the shaft adj-aoent the end on the inner side of upper wall 11d. Cam 53 is attached to the shaft on the outside of the top wall 11d and is secured in place by a clip 56 which is adapted to receive a knob K.

Lever 51 has an arm 510 which projects through an opening 21b in beam 21 and through a rectangular opening 1111 in the top wall 11d of the housing and engages and follows the periphery of cam 53 by reason of the reaction of beam 21 against the lever. Rotation of cam 53 causes lever 51 to rotate about is pivots 51a, 51b one way or the other and to deflect beam 21 to vary the loading on power element 20. Lever 51 also has parallel side arms 51d, 51:: which rise and engage the underside of beam 21 as the lever is "rotated to its extreme clockwise position, as is explained more fully hereinafter.

Cam 53 is shaped genera-11y in the form of a helix, having a relatively short radius at 53a adjacent a radially extending shoulder 53b, and a high plateau 53c terminating in a radially extending shoulder 5311. The rotation of cam 53 is limited by shoulders 53b and 53d abutting opposite sides of arm 510 when the cam is rotated in opposite directions. When cam 53 is rotated to engage shoulder 53d against arm 51c, lever 51 is moved clockwise about pivots 51a, as viewed in FIG. 7, which applies a maximum of force through beam 21 countering the expansion of bellows 20, and arms 51d and 516 engage the undersi-des of laterally projecting side lugs 57 on the central portion of the beam and on opposite sides of stud 20a of power element 20, which arms force the beam and bellows to a position in which switch 13 is held open irrespective of pressures developed in the power element, which pressure will not become excessive due to the limited fill of the power element.

As cam 53 is rotated to move stop shoulder 53b toward arm 51c lever 51 is rotated counterclockwise and acting through screw 51b on beam 21 decreases the loading effect of the beam on the power element, thereby lowering the temperatures at which switch 13 is operated. When portion 53a of the cam is engaged by arm 510 the pressures required in the power element or bellows 20 to close the switch are well below temperatures which would normally occur at tube 200, and therefore the switch is effectively set in its off position.

Control device 50 does not have an auxiliary fan control switch.

It will be seen that by my invention, control devices may be provided formed of a relatively few simple parts, easily assembled and which provide a wide range of adjustment and setting for controlling the operation of an air conditioning system or the like to provide both manual and thermostatic operations. It will be understood that other modifications, and adaptations may be made, all falling within the scope of the claims which follow.

We claim:

1. A pressure responsive control device comprising:

(a) ahousing;

(b) an electric switch in said housing including a movable actuating member;

(c) a vapor filled expansible power element;

(d) means interconnecting said power element and said switch actuator comprising a generally flat spring strip having one end supported by said housing at one end of said housing and adjacent to said power element and the intermediate portion thereof engaging said actuator, the other end of said spring having a reversely curved portion adjacent the end of said housing opposite said one'end thereof;

(e) a lever pivoted to an intermediate portion of said housing and having a swingable end extending adjacent to said reversely curved end of said spring;

(f) a thrust member carried by said swingable end of said lever and engaging the reversed portion of said spring;

(g) an arm connected to said lever; and

(h) manually operable means rotatably supported by said housing and engaging said arm for swinging said arm to shift said spring.

2. A pressure responsive control device comprising:

(a) a rectangular box-like housing, one wall of said housing being formed by an insulating block;

(b) an electric switch supported on said block, said switch including a movable switch operating member centrally disposed in said housing;

(-c) an expansible power element supported on the wall of said housing opposite said insulating block and adjacent one end thereof;

(d) a generally flat spring member extending from one end of said housing to the other and engaging said power element adjacent one end thereof and said switch operating member adjacent the central portion thereof, the other end of said spring having a reversely extended portion;

(e) means on an end wall of said housing adjacent said power element forming an abutment for supporting an end of said spring in engagement in the said power element;

(f) a U shape lever in said housing having the ends of v the legs thereof pivotally supported in opposite side walls of said housing and having the yoke portion thereof extending in a direction transversely of said spring;

(g) a screw threaded through said yoke portion and engaging said reversely extended portion of said spring;

(h) an arm extending rigidly from said lever; and

(i) a cam rotatably supported on a wall of said housing and engaged by said arm and operative to move said lever about its pivot and cause said lever to flex said spring.

3. A pressure responsive control device as defined in claim 2 in which said cam comprises a flat disc supported parallel to and adjacent an inside wall of said housing 20 and said periphery is engaged by said arm extending from said yoke.

-4. A pressure responsive control device as defined in claim 2 in which said cam comprises a flat disc supported on the outside of the top wall of said housing and parallel to and adjacent said top wall, said arm projecting from References Cited by the Examiner UNITED STATES PATENTS 3,096,420 7/1963 Dills 200l40 BERNARD A. GILHEANY, Primary Examiner.

G. MAIER, Assistant Examiner. 

1. A PRESSURE RESPONSIVE CONTROL DEVICE COMPRISING: (A) A HOUSING; (B) AN ELECTRIC SWITCH IN SAID HOUSING INCLUDING A MOVABLE ACTUATING MEMBER; (C) A VAPOR FILLED EXPANSIBLE POWER ELEMENT; (D) MEANS INTERCONNECTING SAID POWER ELEMENT AND SAID SWITCH ACTUATOR COMPRISING A GENERALLY FLAT SPRING STRIP HAVING ONE END SUPPORTED BY SAID HOUSING AT ONE END OF SAID HOUSING AND ADJACENT TO SAID POWER ELEMENT AND THE INTERMEDIATE PORTION THEREOF ENGAGEING SAID ACTUATOR, THE OTHER END OF SAID SPRING HAVING A REVERSELY CURVED PORTION ADJACENT THE END OF SAID HOUSING OPPOSITE SAID ONE END THEREOF; (E) A LEVER PIVOTED TO AN INTERMEDIATE PORTION OF SAID HOUSING AND HAVING A SWINGABLE END EXTENDING ADJACENT TO SAID REVERSELY CURVED END OF SAID SPRING; (F) A THRUST MEMBER CARRIED BY SAID SWINGABLE END OF SAID LEVER AND ENGAGING THE REVERSED PORTION OF SAID SPRING; (G) AN ARM CONNECTED TO SAID LEVER; AND (H) MANUALLY OPERABLE MEANS ROTATABLY SUPPORTED BY SAID HOUSING AND ENGAGING SAID ARM FOR SWINGING SAID ARM TO SHIFT SAID SPRING. 